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Unit 1: Atomic Structure and Periodicity

Study guide for CLEP CLEP Chemistry — Unit 1: Atomic Structure and Periodicity. Practice questions, key concepts, and exam tips.

109

Practice Questions

30

Flashcards

5

Key Topics

Key Concepts to Study

electron configuration
periodic trends
quantum numbers
atomic orbitals
nuclear chemistry (alpha/beta/gamma decay, half-life)

Sample Practice Questions

Try these 5 questions from this unit. Sign up for full access to all 109.

Q1MEDIUM

What is the primary factor that determines the ionization energy of an electron in a particular subshell of an atom?

A) The mass of the nucleus
B) The number of electrons in the subshell
C) The type of orbital occupied by the electron
D) The distance of the subshell from the nucleus
E) The spin of the electron in the subshell
Show Answer

Answer: D — Ionization energy is related to the distance from the nucleus and the effective charge of the nucleus, as described by Coulomb's law.

Q2MEDIUM

What is the primary reason that elements in the same group of the periodic table exhibit similar chemical properties?

A) They have the same atomic mass
B) They have the same number of valence electrons
C) They have the same number of protons in the nucleus
D) They have the same number of electron shells
E) They have the same number of electrons in the innermost shell
Show Answer

Answer: B — Elements in the same group have similar chemical properties due to the same number of valence electrons, which determines their reactivity.

Q3MEDIUM

A sample of boron has two naturally occurring isotopes: boron-10 with a mass of 10.013 u and a relative abundance of 19.1%, and boron-11 with a mass of 11.009 u and a relative abundance of 80.9%. What is the average atomic mass of boron?

A) 9.91 u
B) 10.81 u
C) 11.01 u
D) 10.45 u
E) 10.98 u
Show Answer

Answer: B — To calculate the average atomic mass, multiply the mass of each isotope by its relative abundance and sum the results: (10.013 u * 0.191) + (11.009 u * 0.809) = 10.81 u

Q4MEDIUM

What is the principal quantum number of the outermost energy level of a sodium atom?

A) 1
B) 2
C) 3
D) 4
E) 5
Show Answer

Answer: C — 3 is correct because the outermost energy level of a sodium atom is the third energy level, since sodium has 11 electrons and its electron configuration is 1s²2s²2p⁶3s¹.

Q5MEDIUM

A chemist is studying the properties of a newly discovered compound. The chemist creates a model of the compound, including its molecular structure and electron configuration. Which of the following best describes the purpose of creating this model?

A) To determine the exact molecular weight of the compound
B) To identify the chemical properties of the compound at the macroscopic level
C) To develop a new method for synthesizing the compound
D) To confirm the compound's reactivity with other known substances
E) To visualize the particulate-level properties of the compound and make predictions about its behavior
Show Answer

Answer: E — The model helps the chemist understand the compound's properties at the particulate level, making predictions about its behavior.

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Study Tips for Unit 1: Atomic Structure and Periodicity

  • Focus on understanding concepts, not memorizing facts — CLEP tests application
  • Practice with timed questions to build exam-day speed
  • Review explanations for wrong answers — they reveal common misconceptions
  • Use flashcards for key terms, practice questions for deeper understanding

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